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Naming organic compounds can feel like trying to read a secret code, but once you understand the pattern, the whole map lights up. This guide unwraps the complete IUPAC rules for alkanes, cycloalkanes, alkenes and alkynes in a clear, student-friendly way. Whether you're preparing for MDCAT, ECAT or strengthening school concepts, these rules will help you recognize the parent chain, spot substituents, and number every atom with confidence. Here at LearnChemistryByInamJazbi, the aim is to turn complex naming systems into simple learning paths that anyone can follow.

IUPAC Rules for Naming of Alkanes

1. Identify the longest unbroken continuous carbon chain within molecules which acts as Root or Parent chain and its name is retained as prop, but, pent, hex etc.

2. Allocate numerical designations to the carbon atoms within the parent chain from one of its terminal starting where functional group or substituent (an alkyl group) is nearest.

If the identical substituents are attached at the same position from both ends of main carbon chain, numbering can be done from either sides. However, it the identical substituents are attached at different positions, the numbering should be done from the side where the substituent is nearer.

3. Identify the substituents and name them using prefix such as methyl, ethyl, methoxy, chloro, bromo etc. and mention their position in the longest carbon chain.

4. When two different substituents are attached at the same position from either side of the carbon chain, then number the chain from the terminal nearer the substituent that has alphabetical precedence.

5. When two or more identical substituents are attached to the carbon chain, indicate number of each substituents by using the prefixes di-, tri-, tetra-, and so on.

6. When two identical substituents are present on the same carbon atom in the carbon chain, use that number twice.

7. When two chains of equal length compete for selection as the parent chain, choose the chain with the greater number of substituents.

8. Prefix Cyclo is used to name cycloalkanes.

IUPAC Rules for Naming of Cycloalkanes

1. The cyclic structure or ring is considered as P.C.C. till the number of carbon in the ring is same or greater than number of carbon in chain. Prefix Cyclo is used to name cycloalkanes

2. Rest all rules are similar as nomenclature of alkane.

IUPAC Rules for Naming Alkenes, Alkadiene, Alkatriene

Common System

The common name of alkene is alkylene. In common system, alkenes are named by replacing the “ane” ending of corresponding alkanes with “ylene”

For example

Ethylene for ethene, propylene for propene and butylene for butene and so on.

Derived Name

An alternative way of naming alkenes is by considering them as derivatives of ethylene.

For example

IUPAC System

1. Select the longest continuous carbon Root Chain containing both carbons of the double bond (principle functional group) and maximum number of alkyl groups and name it according to the number of carbon atoms it contains, adding ene (suffix) to name of root chain.

2. The selected chain is numbered in such a way that double bond gets the lowest number (irrespective of the location of alkyl radicals.)

3. Indicate the position of double bond by specifying the location of carbon atoms involved in the double bond.

4. If there are more than one double bonds present within the carbon chain they are indicated by adding the prefixes di, tri etc. before the suffix “ene”.

5. If two chains having same number of multiple bonds then check maximum number of carbons to select parent carbon chain. If multiple bonds & carbon both are same then see maximum number of substituent to select parent carbon chain.

Priority Order

Number of multiple bond > Number of carbon > Number of substituent

Alkadiene and Alkapolyenes

When two double bonds are present in a root chain then it is called ALKADIENE (similarly root chain containing 3, 4, 5 double bonds are called Alkatriene, Alkatetraene, Alkapentaene and so forth).

IUPAC Rules for Naming Alkynes

Common System

In common system, the first member of alkyne family is named as acetylene (C2H2). The higher members of alkynes are named by considering them as derivatives of acetylene.

Derived Name

An alternative way of naming alkynes is by considering them as derivatives of acetylene. The name of higher alkynes is derived from acetylene by considering the branched carbon atoms as alkyl radicals.

For example

IUPAC System

1. Select the longest continuous carbon root chain containing both carbons of the triple bond (principle functional group) and maximum number of alkyl groups and name it according to the number of carbon atoms it contains, adding ‘yne’ (suffix) to the name of root chain to indicate the presence of triple bond.

2. The selected chain is numbered in such a way that triple bond gets the lowest number (i.e. the numbering of carbon chain starts from the terminal which is nearest to the carbon-carbon triple bond.

3. Indicate the position of triple bond by specifying the location of the carbon atom involved in the bond.

4. If two or more triple bond are present in the chain then they are indicated by adding the prefix di, tri etc. before the suffix -yne.

Alkadiyne

When two triple bonds are present in a root chain then it is called Alkadiyne.

IUPAC Rules for Naming Alkenynes

1. When a root chain contains both double and triple bonds then it is called Alkenyne. [Its IUPAC name is derived by replacing –ane of parent alkane to –enyne. IN SOME BOOKS, ITS SYSTEMATIC NAME IS WRITTEN AS ALKENEYNE (E.G. BUTENEYNE) WHICH IS WRONG].

2. For Alkenyne root chain when both double and triple bonds are in the molecule at equal positions from the end, then the preference of numbering is given to double bond so as to give lowest number to double bonds (as double bond is prior to triple bond in Priority Functional Group Chart].

3. For alkenyne root chain when double and triple bonds are present in the molecule at different positions, then numbering should start from that end where double or triple bond gets lowest number.

Alkadienyne

Alkadienyne contains 2 double bonds along with 1 triple bond while Alkendiyne contains 2 triple bonds along with 1 double bond.

🌈🧪 Quick Summary: IUPAC, Common & Derived Naming of Alkanes, Cycloalkanes, Alkenes and Alkynes

🔷 1. Alkanes (Saturated Hydrocarbons)

General formula: CₙH₂ₙ₊₂
Bonding: All single bonds
Suffix: -ane

🟢 IUPAC Naming Steps

✴️Find longest carbon chain
✴️Number from nearest substituent
✴️Name substituents (methyl, ethyl etc.)
✴️Use prefixes (di, tri…) if repeated
✴️Combine: prefix + parent + suffix

🧁 Common Names (Derived Names)

✨CH₄ → Methane
✨C₂H₆ → Ethane
✨C₃H₈ → Propane
✨C₄H₁₀ → Butane
✨(CH₃)₄C → Neo-pentane
✨(CH₃)₃CH → Iso-butane

🌈 Examples

✨CH₃CH₂CH₂CH₃ → Butane
✨CH₃CH(CH₃)CH₃ → 2-methylpropane
✨CH₃CH₂CH(CH₃)CH₃ → 2-methylbutane

🔶 2. Cycloalkanes

General formula: CₙH₂ₙ
Structure: Ring
Prefix: cyclo-
Suffix: -ane

🧿 Rules

✴️Number ring to give lowest numbers to substituents
✴️If only one substituent → no numbering

🌼 Examples

✨C₅H₁₀ ring → Cyclopentane
✨CH₃–cyclohexane → Methylcyclohexane
✨Two substituents → 1,3-dimethylcyclobutane

🔷 3. Alkenes (Double-bond Hydrocarbons)

General formula: CₙH₂ₙ
Bonding: At least one C=C
Suffix: -ene

🔥 IUPAC Rules

✴️ Select longest chain containing C=C
✴️Number from the end closest to the double bond
✴️Mention position of double bond
✴️Add substituents

🌟 Examples

✨CH₂=CH₂ → Ethene
✨CH₃CH₂CH=CH₂ → 1-butene
✨CH₃CH=CHCH₃ → 2-butene
✨Branched: CH₂=C(CH₃)₂ → 2-methylpropene

🔷 4. Alkynes (Triple-bond Hydrocarbons)

General formula: CₙH₂ₙ₋₂
Bonding: C≡C
Suffix: -yne

🔥 Rules

✴️Chain must include triple bond
✴️Number from nearest end to the triple bond
✴️Add substituent names

🌙 Examples

✨CH≡CH → Ethyne (Acetylene)
✨CH₃C≡CH → Propyne
✨CH₃CH₂C≡CCH₃ → 2-pentyne

🌀 5. Mixed Systems (Double + Triple Bonds)

Priority order:
Double bond = Triple bond
But name as ene-yne; double bond gets lower locant if tie.

Example

CH₂=CH–C≡CH → 1-buten-3-yne

🧪🔥 20-Question Quiz (IUPAC + Common Names)

(Answers given below)

MCQs / Short Answers

💠1. Name: CH₃CH₂CH₂CH₃
💠2. Give IUPAC of iso-butane
💠3. Give IUPAC: (CH₃)₃CCH₃
💠4. Name: CH₃CH(CH₃)CH₂CH₃
💠5. IUPAC of neopentane
💠6. Name: CH₂=CHCH₃
💠7. Name: CH₃CH₂CH=CH₂
💠8. Give IUPAC: CH₃C≡CCH₃
💠9. Common name of ethyne
💠10. Name: CH₃CH₂C≡CH
💠11. IUPAC: CH₃CH₂CH(CH₃)CH=CH₂
💠12. Name this ring: C₆H₁₂ (all single bonds)
💠13. Name: 1,2-dimethylcyclopropane
💠14. Give IUPAC: CH₃CH=CHCH₂CH₃
💠15. Name: CH₃CH₂C(CH₃)₂CH₃
💠16. IUPAC: CH₃CH₂C≡CCH₂CH₃
💠17. Common name of CH₃–CH(CH₃)–CH₃
💠18. Name: CH₂=CH–C(CH₃)₃
💠19. Identify: triple bond + 5 carbons → ?
💠20. Name: CH₃C(CH₃)=CH₂

🎯 Answers Key

Butane
2-methylpropane
2,2-dimethylpropane
2-methylbutane
2,2-dimethylpropane
Propene
1-butene
2-butyne
Acetylene
1-butyne
4-methylpent-1-ene
Cyclohexane
Correct as written
2-pentene
3,3-dimethylpentane
2-hexyne
Isobutane
3-methylprop-1-ene
Pentyne
2-methylprop-1-ene

🔥 Difficult MDCAT Quiz 🎯

1. The correct IUPAC name of (CH₃)₂CHCH₂CH=CH₂ is:

🟥 A. 5-methylhex-1-ene
🟦 B. 3-methylhex-1-ene
🟩 C. 4-methylpent-1-ene
🟨 D. 3-methylpent-1-ene

2. Identify the correct name of CH₃C≡CCH(CH₃)₂

🟥 A. 4-methylpent-2-yne
🟦 B. 3-methylpent-1-yne
🟩 C. 2-methylpent-3-yne
🟨 D. 3-methylpent-2-yne

3. The IUPAC name of neohexane is:

🟥 A. 2,2-dimethylbutane
🟦 B. 2,3-dimethylbutane
🟩 C. 2,2-dimethylpentane
🟨 D. 3,3-dimethylpentane

4. Correct name of CH₂=CHCH₂C(CH₃)₃

🟥 A. 4,4-dimethylpent-1-ene
🟦 B. 3,3-dimethylpent-1-ene
🟩 C. 3,3-dimethylhex-1-ene
🟨 D. 4,4-dimethylhex-1-ene

5. Which is the correct name for CH₃CH₂C(CH₃)₂CH₂CH₃?

🟥 A. 4,4-dimethylpentane
🟦 B. 3,3-dimethylpentane
🟩 C. 2,2-dimethylhexane
🟨 D. 3,3-dimethylhexane

6. Name the compound: CH≡C–CH₂–CH(CH₃)₂

🟥 A. 4-methylpent-1-yne
🟦 B. 3-methylpent-1-yne
🟩 C. 4-methylhex-2-yne
🟨 D. 3-methylhex-1-yne

7. Correct IUPAC name of isobutylene is:

🟥 A. 2-methylpropene
🟦 B. 2-methylpropane
🟩 C. 1-methylpropene
🟨 D. 3-methylpropene

8. For CH₃CH₂CH₂C≡CCH₃, the correct name is:

🟥 A. 2-hexyne
🟦 B. 3-hexyne
🟩 C. 4-hexyne
🟨 D. 1-hexyne

**9. Which is the correct name of this ring?

Two methyl groups on C-1 and C-3 of cyclohexane.**
🟥 A. 1,3-dimethylcyclohexane
🟦 B. 3,5-dimethylcyclohexane
🟩 C. 1,4-dimethylcyclohexane
🟨 D. 2,4-dimethylcyclohexane